i started reading the manual and realised I had to resolve another issue first namely how do I configure iis for visual studio 2008 whcih i use on for development on my laptop as this is required to install the filter. I'd rather do this first before
going "online", configuraiton of iis does not seem to appear in the vs2008 ide. strange!

...matches any URL that begins with /0.4/. Because you don't have an "end of line" symbol on that pattern, it matches anything and regardless of what comes after '/0.4/', if anything, the URL gets rewritten.

If you want to just rewrite the short URL /0.4/ to default.aspx, then just append the $ to the pattern:

RewriteRule ^/0.4/$ /0.4/default.aspx

But I would want to make the slash optional also. Hence:

RewriteRule ^/0.4/?$ /0.4/default.aspx

The question mark in the pattern above is a quantifier, saying "zero or one of the previous thing". And the
previous thing is the slash. So that pattern matches /0.4 and /0.4/, but not /0.4/hello.

Your other two rules should work just fine. (Notice that they already have the $ as the terminating symbol in the pattern)